Jessica Biel and Justin Timberlake put that theory to the test during a beach getaway to Puerto Rico last week. The pair hung out at the water's edge July 15, where they played a game of paddleball.

Biel, 30, sported a skintight, white wetsuit top and showed off her toned derriere in tiny black bathing suit bottoms as she hit the ball back and forth with her shirtless fiancee, 31, who rocked boardshorts.

"For me, getting enough sleep, drinking lots of water, having a healthy diet and staying away from alcohol are musts," she told ELLE last June. "It's so boring, I know, but doing those things really helps."

When it comes to her workouts, she's also a big believer in mixing up her routine by alternating between boxing, martial arts and yoga. "Yoga is a constant for me because it keeps my muscles long and flexible," she explained to the mag. And when the weather heats up? Biel says she makes time to hang out in the sun, "playing volleyball and jogging with my dog, Tina."